Unable to get callback from function - node.js

Question

Trying to get the variable random_song from the function functions.random_song
Function:
functions.random_song = () => {
fs.readFile('auto_playlist.txt', 'utf8', function(err, data) {
if (err) {
console.log(`${`ERR`.red} || ${`Error fetching song from auto playlist ${err}`.red}`);
}
let songs = data.split('\n');
songs.splice(-1, 1);
var random = Math.floor(Math.random()*songs.length);
let random_song = (songs[random]);
return random_song;
})
}
Attempting to callback the random song
functions.random_song(song => {
console.log(song)
})
The code just return undefined Ideas?

Answer 1

Your function:
functions.random_song = (callback) => {
fs.readFile('auto_playlist.txt', 'utf8', function(err, data) {
if (err) {
// Do stuff
return callback(err);
}
// Do stuff
callback(null, random_song);
})
}
And then call it:
functions.random_song((err, song) => {
// Do stuff
});
You may want to read more about using Promise/async-await instead of callback.

Answer 2

functions.random_song = () => {
let data = fs.readFileSync('auto_playlist.txt', 'utf8');
let songs = data.split('\n');
songs.splice(-1, 1);
var random = Math.floor(Math.random()*songs.length);
let rand_song = (songs[random]);
return rand_song;
}
console.log(functions.random_song())
got it working, thanks for the help <3

Answer 3

Following is the code which use Promise to handle file read and data processing task asynchronously
const fs = require('fs')
const functions = {}
functions.random_song = () => {
return new Promise((resolve, reject) => {
fs.readFile('auto_playlist.txt', 'utf8', function(err, data) {
if (err) {
console.log(err)
reject(err)
}
let songs = data.split('\n');
songs.splice(-1, 1);
var random = Math.floor(Math.random()*songs.length);
let random_song = (songs[random]);
resolve(random_song);
})
})
}
functions.random_song()
.then(song => console.log('Song Name', song))
.catch(err => console.error('Error fetching songs', err))
console.log('It will be executed before promise is resolved')

Answer 4

fs.readFile is asynchronus and your function will return before the file is read. Use fs.readFileSync instead. Like this:
functions.random_song = () => {
const data = fs.readFileSync('auto_playlist.txt', 'utf8');
let songs = data.split('\n');
songs.splice(-1, 1);
var random = Math.floor(Math.random()*songs.length);
let random_song = (songs[random]);
return random_song;
}